A development device such as a development cartridge for use in an image forming apparatus may be configured to comprise a lower frame and an upper frame wherein the lower frame includes right and left sidewalls, and bottom and rear walls which connect the right and left sidewalls. When the upper frame is welded on an upper surface of the lower frame (i.e., upper surfaces of the right and left sidewalls and the rear wall), an opening and a toner reservoir are formed therein.
In such a development device, a boss and a corresponding boss hole may be formed on an upper surface of each sidewall of the lower frame and in the upper frame, respectively, so that the boss and the boss hole are engaged with each other to place the upper and lower frames in alignment.
In order to provide sufficient areas of faying surfaces of the both frames, it may be preferable that the boss or like structures formed on the upper surface (i.e., faying surface) of the lower frame be dispensed with. Sufficient areas of faying surfaces could be made on the upper surface of the lower frame by thickening part of the sidewalls of the lower frame; however, this would disadvantageously increase the size of the development device.
There is a need to provide a developing device in which the size of the device can be reduced while ensuring that sufficient areas of the faying surfaces are provided.